The present invention relates to a thermal expansion valve equipped in a refrigeration system of an air conditioner for a vehicle and the like for controlling the flow of refrigerant being provided to an evaporator according to the temperature of the refrigerant.
FIG. 3 is an explanatory view showing the vertical cross-section of the structure of a conventionally known thermal expansion valve.
A thermal expansion valve shown as a whole by reference number 1 comprises a square column shaped valve body 10 made of aluminum alloy and the like. The valve body 10 comprises a passage 20 for receiving a high-pressure refrigerant transmitted from a compressor of the air conditioner, and a valve chamber 22 formed to the lower portion of the valve body 10 that communicates with the passage 20.
The valve chamber 22 communicates the passage 20 with a passage 26 via a valve seat 24, and the refrigerant is sent out through the passage 26 toward an evaporator.
Within the valve chamber 22 is equipped a spherical valve means 30 that opposes against the valve seat 24, and the valve means 30 is supported by a valve means support member 32. The valve means support member 32 is supported via a spring 34 by a nut member 36 functioning as an adjustment screw. The nut member 36 is screwed onto the valve body 10 at a screw thread portion 37 by a tool such as a wrench and the like utilizing a hexagon hole 38 formed thereto.
By adjusting the depth of the nut member 36 being screwed onto the valve body, the spring force of the spring 34 supporting the valve means 30 can be controlled so that the valve means 30 is biased toward the direction closing the valve. A seal member 39 is fixed to the nut member 36, thus preventing the refrigerant from leaking out of the valve chamber 22.
The valve body 10 contains a return passage 28 of the refrigerant returning from the evaporator toward the compressor, formed in parallel with the passage 26.
The valve means 30 is operated through a working rod 40 that penetrates the center portion of the valve body 10. The working rod 40 is a small-diameter rod made of stainless steel and the like, the upper end thereof being inserted to a stopper member 50 and the lower end coming into contact with the valve means 30.
A seal member 42 is equipped between the working rod 40 and the valve body 10, which constitutes a seal between the passage 26 through which the refrigerant is sent out and the passage 28 through which the refrigerant returns.
The stopper member 50 is equipped within a driving device so-called a power element and shown as a whole by reference number 60.
The power element 60 comprises a disc-shaped can body 62 defined by an upper lid 621 and a lower lid 622, the can body 62 being screwed onto the upper portion of the valve body 10 via a screw thread 64 formed to the lower lid 622, and the periphery of the stopper member 50 being supported by the lower lid 622.
The can body 62 contains a diaphragm 66, and the periphery of the diaphragm is sandwiched between the upper lid 621 and the lower lid 622, which are fixed to each other by welding, defining an upper pressure chamber 68 and a lower pressure chamber 69. A working fluid is filled within the upper pressure chamber 68, and is sealed by a plug body 70.
The pressure of the refrigerant passing through the return passage 28 of the refrigerant operates on the lower surface of the stopper member 50, and the temperature of the refrigerant is transmitted via the working rod 40 to the stopper member 50, and further transmitted via the diaphragm 66 to the working fluid within the upper pressure chamber 68.
The diaphragm 66 is displaced by the pressure within the upper pressure chamber 68, the amount of displacement thereof moving the valve means 30 through the working rod 40, thus decompressing and expanding the refrigerant flowing through the passage 20, adjusting the opening area of the orifice passage constituting the valve seat 24, and controlling the flow of refrigerant traveling toward the evaporator.
In such conventional thermal expansion valve, the structure requires a large number of parts including the valve receiving member, the spring and the adjustment screw, making it difficult to reduce the size and the weight of the thermal expansion valve.
Moreover, a problem sometimes occurs according to the prior art valve in which the refrigerant leaks out of the valve chamber through the adjustment screw portion.
Considering these points, the object of the present invention is to provide a thermal expansion valve having a simplified structure and smaller number of parts being required, thus enabling to correspond to the desired reduction of size and weight of the car air conditioner.
In order to achieve the above objects, the present invention provides a thermal expansion valve comprising a valve body, a first passage formed to the valve body through which high pressure refrigerant travels, a valve chamber formed within the first passage, a second passage formed to the valve body in parallel with the first passage through which refrigerant traveling toward an evaporator travels, an orifice passage to which a valve seat member is press fit for communicating the valve chamber with the second passage, a valve means positioned opposing the orifice passage, a third passage through which refrigerant being sent out of the evaporator travels, and a temperature sensing rod for sensing the temperature of the refrigerant traveling through the third passage and driving the valve means according thereto; characterized in that the valve seat member is mounted between the working rod and the valve means in advance before it is fixed to the orifice passage, and the opening area of the orifice passage is adjusted by the displacement of the valve means.
Further, the above working rod comprises a small-diameter portion being inserted to the valve seat member, and having a spherical valve means fixed to the end of the small-diameter portion.
Moreover, the present valve is equipped with a spring that biases the working rod toward the diaphragm.